Beryllium-copper alloy excellent in strength, workability and heat resistance and method for producing the same

ABSTRACT

In the present invention, in order to minimize the amount of deformation due to heat treatment, the content of Be is lowered than the conventional ones, and the decrease in strength accompanied by decreasing Be, is compensated by dissolving strengthening of Si and Al, and precipitation strengthening of intermetallic compounds NiBe and CoBe. Further, by precipitating such intermetallic compounds, workability and heat resistance are also improved simultaneously and aging treatment conditions are also made flexible. Thus, according to the present invention, a beryllium-copper alloy having excellent strength, workability and heat resistance, can be provided economically, and particularly as for aging materials, users&#39; burden can be markedly decreased.

TECHNICAL FIELD

The present invention relates to beryllium-copper alloys used aselectrically conductive spring materials for lead frames, terminals,connectors, relays, switches, jacks and the like, of which suchproperties as strength, workability and stress-relaxation are important,and a method for producing the same.

BACKGROUND ART

Beryllium-copper alloys containing 0.2 to 0.3% by weight of Be in copperhave been known heretofore as electrically conductive spring materialsand disclosed in Japanese Patent Examined Publication No. 4-53936 by thepresent applicant. As such beryllium-copper alloys, there are agingmaterials of which an aging treatment is performed by users, andmill-hardened materials of which aging treatment have been appliedbefore shipping.

Recently, due to an enhanced miniaturization of electronic parts, higherstrength is required also for beryllium-copper alloys. The materials tobe obtained are disclosed in JIS C 1720 (Be 1.8 to 2.0% by weight).

However, in these aging materials of such beryllium-copper alloys, therehave been disadvantages that deformation is likely to occur during agingtreatment and also setting up of treating conditions is difficult due tonarrow tolerance of aging treatment conditions. Therefore, there hasbeen a problem that it is not necessarily easy to attain the desiredcharacteristics by aging treatment at the user's side. Also, in theconventional mill-hardened material of beryllium-copper alloys, therehave been problems that a sufficient workability cannot be obtained and,in particular, bending workability is poor in a direction perpendicularto the direction of rolling. Further, as to heat resistance that can beregarded as an index of long-term reliability, there has been a problemthat stress-relaxation ratio is large, Incidentally, thestress-relaxation ratio is a value indicating reduction Of springproperties for a long period of time and the measuring method thereof isregulated in EMAS (Japan Electronic Manufacturers AssociationStandard)-3003 as "Testing Method of Stress-Relaxation by Bending ofSpring Materials". According to this standard, the stress-relaxation isdefined as a phenomenon that the stress generated in materials under aconstant strain decreases slowly with a lapse of time.

DISCLOSURE OF THE INVENTION

The present invention has been developed to address above-mentionedconventional problems. It is an object of the invention to provide aberyllium-copper alloy which is excellent in strength as a matter ofcourse, which can be used as an aging material having a wide toleranceof the aging treatment conditions, i.e., flexible treatment conditionsso as to reduce the burden at the user end by making deformation at theaging treatment difficult, and which can be also used as a mill-hardenedmaterial having excellent workability and heat resistance. It is afurther object of the invention to provide an advantageous method forproducing the same.

According to the present invention, there is provided a beryllium-copperalloy excellent in strength, workability and heat resistance, having acomposition containing

Be: 0.5 to 1.5% by weight,

at least one member selected from the group of Ni and Co: 0.3 to 1.5% byweight,

at least one member selected from the group of Si and Al; 0.5 to 2.5% byweight,

and the balance being substantially Cu, said alloy containing as anintermetallic compound NiBe or/and CoBe in the range of 0.20 to 0.90% byweight, and at least 45% thereof being present as fine particles havinga diameter of 0.1 μm or less.

Also, the present invention provides a method for producing aberyllium-copper alloy which is excellent in strength, workability andheat resistance, and which comprises subjecting to hot working andsubsequent cold working a cast material having a composition containing

Be: 0.5 to 1.5% by weight,

at least one member selected from the group of Ni and Co; 0.3 to 1.5% byweight,

at least one member selected from the group of Si and Al; 0.5 to 2.5% byweight,

and the balance being substantially Cu, subsequently subjecting thematerial to a solution treatment at a temperature of 800° C. or higher,cooling at a rate of 20° C./s or more between the temperature range ofat least 800° C. to 600° C., subsequently subjecting the material tofinishing working of 5 to 40%, and then applying aging treatment to thematerial at a temperature of 300° to 460° C.

In the present invention, strength, workability and heat resistance tobe attained as target are as follows.

First, as to strength, it should satisfy a tensile strength of 84 to 115kgf/mm².

As for workability, at the tensile strength of 84 to 97 kgf/mm², whenbending work is performed with a R/t ratio (R: bending radius, t: platethickness) of 1.0, it should be possible to perform good work in anydirection with respect to the direction of rolling.

Further, as to heat resistance, that is, a heat treatment deformationamount, a deformed amount (change in warpage amount) of a materialbefore and after aging treatment of a material having a size of 20 mm×20mm, and a plate thickness of 0.3 mm should be 10 μm or less.

Furthermore, flexibility of the heat treatment conditions in accordancewith the present invention should be such that a fluctuation of atensile strength is within the range of ±8 kgf/mm² even when optionalaging conditions are selected.

In the following, the present invention will be explained specifically.

The first characteristic feature of the beryllium-copper alloy of thepresent invention resides in that, in order to reduce deformation due toheat treatment, the content of Be is made 1.5% by weight or less whichis markedly reduced as compared with the conventional beryllium-copperalloy. Nevertheless, when the content of Be is less than 0.5% by weight,strength is insufficient since a strengthening mechanism is noteffective. Accordingly, in the present invention, the content of Be islimited in the range of 0.5 to 1.5% by weight. Incidentally, a morepreferred range of Be is 0.7 to 1.3% by weight, and further preferredrange is 0.9 to 1.1% by weight.

The second characteristic feature of the beryllium-copper alloy of thepresent invention resides in that lowering in strength accompanied bydecreasing the content of Be as mentioned above is compensated bycomposite addition of Si, Al and Ni, Co.

First, explanation will be made of Si and Al. These are each dissolvedin the Cu mother phase as a solid solution and contribute to improvementin strength by solid solution strengthening mechanism. However, whentheir content is less than 0.5% by weight, strength and workability areinsufficient, while when the content exceeds 2.5% by weight,conductivity, rolling workability and soldering property are lowered andalso deformation due to heat treatment is promoted. Accordingly, Al andSi are to be contained in the range of 0.5 to 2.5% by weight in eithercase of single use or in combination. A more preferred range is 1.0 to2.5% by weight, and a further preferred range is 1.5 to 2.5% by weight.

Next, explanation will be made of Ni and Co. These precipitate in the Cumother phases as an intermetallic compound such as NiBe or CoBe, etc.,and contribute to improvement in strength due to their precipitationstrengthening mechanisms. And yet, by precipitation of such anintermetallic compounds heat resistance, etc. are also improved.

When precipitation strengthening is intended by an intermetalliccompound mainly comprising the above-mentioned NiBe or CoBe, if thecontent of Ni or/and Co is less than 0.3% by weight, not only isstrength lowered but also grain size becomes coarse whereby workabilitybecomes poor. On the other hand, when the content of Ni or/and Coexceeds 1.5% by weight, the amount of the intermetallic compound formedbetween Be, Si, Al, etc. increases whereby bending workability becomespoor. Accordingly, Ni and Co should be contained in the range of 0.3 to1.5% by weight in either case, whether used alone or in combination. Amore preferred range is 0.3 to 1.1% by weight, and a further preferredrange is 0.3 to 0.7% by weight.

Also, it is necessary that the amount of NiBe, CoBe intermetalliccompounds to be precipitated, is in the range of 0.20 to 0.90% byweight. The reason is that when the content is less than 0.20% byweight, sufficient strength cannot be obtained, while when it exceeds0.90% by weight, bending workability is markedly lowered and heatresistance is also lowered. Accordingly, a more preferred amount of theintermetallic compound mainly comprising NiBe and CoBe is in the rangeof 0.20 to 0.60% by weight when it is used as a mill-hardened material,whereas it is in the range of 0.30 to 0.75% by weight when it isprovided as an aging material.

Further, in the NiBe and CoBe intermetallic compounds, a size of theprecipitate, i.e., a grain size is important. The reason is that evenwhen the content of the intermetallic compounds satifies theabove-mentioned preferred range, if the ratio of grains exceeding 0.1 μmis large, cracks will likely be generated upon working based on suchcoarse grains. Thus, in the present invention, as for the intermetalliccompound, at least 45% of the compound should be contained as fineparticles with a diameter of 0.1 μm or less.

As stated above, in the present invention, in order to make compatibleall of strength, bending workability and heat resistance, etc.,characteristics such as strength and bending workability, etc. areimproved by Be, Si and Al. Also, in the present invention, in order tosuppress deformation in the shape of the material during agingtreatment, an amount of Be is decreased. As for lowering in strengthaccompanied by decrease in Be, properties are improved by precipitationstrengthening of the intermetallic compounds mainly comprising NiBe andCoBe, and solid solution strengthening owing to Si, Al and the like.

Incidentally, among the intermetallic compounds mainly comprising NiBeand CoBe, an intermetallic compound such as NiAl₃, NiSi, etc. are alsoincluded in a little amount.

Also, in addition to the above-mentioned components, Fe, Ti, Cr, etc.,may be added as a sub-component in the range of 0.05 to 0.5% by weight.These are components each of which contributes to improve strength, andparticularly, Fe and Si are components which also contribute to improveworkability.

The third characteristic feature of the beryllium-copper alloy of thepresent invention resides in that heat treatment conditions are madeflexible. The reason is that the precipitation temperature of NiBe orCoBe has an extremely wide temperature range of 300° to 460° C., and thetreatment time also has an extremely wide range of 15 minutes to 6hours. And yet, even when in such wide treatment conditions, thevariation range of tensile strength can be made within the range of ±8kgf/mm².

As a result, the aging treatment at the user side becomes markedly easyas compared with prior art and the user's burden can be remarkablyreduced.

Next, preferred preparation conditions of the present invention will beexplained.

To the cast piece prepared by the above-mentioned preferred compositionrange of components is subjected hot working and cool working. The alloyof the present invention has essentially good hot workability and coolworkability as long as it satisfies the above-mentioned compositionrange of the components.

Then, a solution treatment is carried out in order that elements formingintermetallic compounds such as NiBe, CoBe, etc. are sufficientlydissolved in the mother phase as a solid solution. In this solutiontreatment, if the treatment temperature is less than 880° C.,dissolution of elements forming intermetallic compounds into the alloybecomes insufficient and bending workability of the product becomespoor, so that it is necessary to set the solution treatment temperatureat 880° C. or higher.

After the above solution treatment, the alloy is cooled to normaltemperature. In the present invention, with regard to such a coolingtreatment, it is important to carry out the cooling at a rate of 20°C./s or more, for at least the temperature range of 800° C. to 600° C.The reason is that the temperature range of 800° to 600° C. is a rangein which intermetallic compounds such as NiBe, CoBe, etc., are likelyprecipitated with a coarse grain. Thus, if the cooling rate is slowerthan 20° C./s, most part of the intermetallic compounds precipitates ascoarse grains, and as a result, precipitation of fine grains with asufficient amount in the subsequent aging treatment cannot be expected.Such coarse grains make workability poor. Accordingly, in the presentinvention, after the solution treatment, the cooling should be carriedout at a rate of 20° C./s or more for at least the temperature range of800° to 600° C. More preferably, it is 40° C./s or more.

Incidentally, the above-mentioned quenching treatment after the solutiontreatment is not limited only to the temperature range of 800° to 600°C., but it is needless to say that the same quenching treatmentthereafter, for example, until at room temperature, is advantageous formaintaining a sufficient amount of solid solution of the elements forforming an intermetallic compound.

Here, as for cooling means, any means are effective as long as theabove-mentioned cooling rate can be ensured, and it is not particularlylimited. Thus, water cooling, mist cooling, gas cooling, etc. areparticularly advantageously adopted.

Then, finishing work is carried out to finish the alloy to a shape of aproduct. At this time, if the working ratio is less than 5%, sufficientstrength cannot be obtained, while if it exceeds 40%, bendingworkability deteriorates so that the working ratio is limited to therange of 5 to 40%. More preferred working ratio is 10 to 20%.

Subsequently, an aging treatment is carried out to precipitate a desiredintermetallic compound.

Here, when the aging temperature is less than 300° C., sufficientstrength cannot be obtained or, even when obtained, bending workabilitydeteriorates. On the other hand, if it exceeds 460° C., bendingworkability also deteriorates. Thus, it is necessary to set the agingtemperature in a range of 300° to 460° C. Also, the aging time can beselected from a wide range of 15 min to 6 hours. More preferred agingtreatment conditions are the temperature of 320° to 380° C. and the timeof 20 min to 3 hours, and further preferred treatment conditions are thetemperature of 330° to 360° C. and the time of 1 to 3 hours.

Thus, it is possible to obtain a beryllium-copper alloy which deformslittle during heat treatment at an aging treatment, has flexible agingtreatment conditions, and yet has excellent strength, bendingworkability and heat resistance.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a graph showing the relationship between aging treatment timeand tensile strength of the obtained product, with an aging treatmenttemperature as a parameter.

BEST MODE FOR CARRYING OUT THE INVENTION Example 1

This example relates to mill-hardened materials, in which cast pieces ofberyllium-copper alloys having the compositions each shown in Tables 1to 7 were subjected to solution treatment, finishing working and thenaging treatment under the conditions shown in these Tables to prepareproducts.

The results were examined for stress relaxation ratio, hardness, tensilestrength and bending workability of the thus obtained products, and arealso shown in Tables 1 to 7 with overall evaluations.

Incidentally, the bending workability was judged visually by subjectinga test specimen having a plate thickness of 0.3 mm to bending workingusing a bending tool so that the inner bending radius come to 0.3 mm,(R/t ratio=1.0) in accordance with JIS Z 2248, then the bent surface wasobserved by magnifying it by 30 times. The directions of bending weremade parallel direction (0°) and perpendicular direction (90°) to thedirection of rolling, and expressed by ⊚: not rough, ◯: a little rough,Δ: markedly rough, x: cracks, and xx: rupture.

Also, as to data for the amounts of material deformation, smallspecimens with a size of 20×20 mm were cut from the material having aplate thickness of 0.3 mm in both longitudinal and width directions, andthe amounts of curvature were measured before and after heat treatment.For measurement of the amounts of curvature, a non-contact type shapemeasuring device was used.

Further, as for the heat resistance, among the properties of thematerials thus obtained, the stress relaxation ratio (permanentdeformation amount) was obtained by the measure using the cantileverbeam method at the time of loading the stress of 80% or less of 0.2%proof stress at 200° C. for 100 hours.

                                      TABLE 1                                     __________________________________________________________________________    Mill-hardened materials                                                                  Examples                                                           Number     1   2   3   4   5   6   7                                          __________________________________________________________________________    Composition wt %                                                              Be         0.9 0.7 1   0.9 1.11                                                                              1.11                                                                              1.29                                       Ni         0.6 0.8 0.87                                                                              0.8 0.27                                                                              0.4 0.6                                        Co         0   0.07                                                                              0   0.07                                                                              0.6 0.47                                                                              0.27                                       Al         0.5 1.5 1   1   0.9 0.2 0.5                                        Si         0.3 0.8 0   0   0.5 1   0.5                                        NiBe + CoBe                                                                              0.69                                                                              1.00                                                                              1.00                                                                              1.00                                                                              1.00                                                                              1.00                                                                              1.00                                       (theoretical value)                                                           NiBe + CoBe                                                                              0.39                                                                              0.82                                                                              0.54                                                                              0.52                                                                              0.57                                                                              0.60                                                                              0.67                                       (precipitated amount)                                                         Ratio of fine                                                                            92  48  62  71  60  58  51                                         particle (%)                                                                  Preparation                                                                   conditions                                                                    Solution treatment                                                                       910 905 900 910 900 900 885                                        temperature (°C.)                                                      Cooling temperature*                                                                     45  25  30  35  30  30  25                                         (°C./s)                                                                Aging temperature                                                                        340 360 345 350 345 345 340                                        (°C.)                                                                  Aging time (min)                                                                         20  80  15  10  15  20  15                                         Working ratio (%)                                                                        15  20  20  20  20  20  25                                         Properties                                                                    Stress relaxation                                                                        10  12  13  14  15  14  18                                         ratio (%)                                                                     Hardness (Hv)                                                                            241 288 247 245 285 272 276                                        Tensile strength                                                                         84.5                                                                              94.6                                                                              86.7                                                                              86  94.2                                                                              95.4                                                                              96.8                                       (kgf/mm.sup.2)                                                                Bending workability                                                                      ⊚                                                                  Δ                                                                           ⊚                                                                  ⊚                                                                  ◯                                                                     ◯                                                                     Δ                                    (0°)                                                                   Bending workability                                                                      ⊚                                                                  Δ                                                                           ⊚                                                                  ⊚                                                                  ◯                                                                     ◯                                                                     Δ                                    (90°)                                                                  Overall evaluation                                                                       very                                                                              good                                                                              very                                                                              very                                                                              very                                                                              very                                                                              good                                                  good    good                                                                              good                                                                              good                                                                              good                                           __________________________________________________________________________     *Note:                                                                        Cooling temperature at the temperature region of 800 to 600° C.   

                                      TABLE 2                                     __________________________________________________________________________    Mill-hardened materials                                                                  Examples                                                           Number     8   9   10  11  12  13  14                                         __________________________________________________________________________    Composition wt %                                                              Be         1.29                                                                              0.9 0.9 1.11                                                                              1.11                                                                              0.7 0.7                                        Ni         0   1.05                                                                              0   0.5 0.5 0.2 0.4                                        Co         0.87                                                                              0   1.05                                                                              0.55                                                                              0.55                                                                              0.3 0.1                                        Al         1.5 0.5 0.8 0   1   2   0.5                                        Si         0.9 1.2 0   0.6 1.1 0.2 0.9                                        NiBe + CoBe                                                                              1.00                                                                              1.00                                                                              1.21                                                                              1.21                                                                              1.21                                                                              0.58                                                                              0.58                                       (theoretical value)                                                           NiBe + CoBe                                                                              0.65                                                                              0.79                                                                              0.72                                                                              0.72                                                                              0.77                                                                              0.41                                                                              0.40                                       (precipitated amount)                                                         Ratio of fine                                                                            53  55  61  72  49  60  70                                         particle (%)                                                                  Preparation                                                                   conditions                                                                    Solution treatment                                                                       890 900 915 905 895 905 910                                        temperature (°C.)                                                      Cooling temperature*                                                                     25  25  30  35  25  30  35                                         (°C./s)                                                                Aging temperature                                                                        340 360 360 350 350 340 340                                        (°C.)                                                                  Aging time (min)                                                                         15  15  10  20  30  35  20                                         Working ratio (%)                                                                        35  30  18  36  25  20  20                                         Properties                                                                    Stress relaxation                                                                        18  14  15  17  13  14  16                                         ratio (%)                                                                     Hardness (Hv)                                                                            290 284 251 255 287 288 251                                        Tensile strength                                                                         95.9                                                                              96.6                                                                              88  89.5                                                                              93.6                                                                              94.2                                                                              88.1                                       (kgf/mm.sup.2)                                                                Bending workability                                                                      ◯                                                                     Δ                                                                           ◯                                                                     ◯                                                                     Δ                                                                           ◯                                                                     ⊚                           (0°)                                                                   Bending workability                                                                      Δ                                                                           Δ                                                                           Δ                                                                           ◯                                                                     Δ                                                                           Δ                                                                           ⊚                           (90°)                                                                  Overall evaluation                                                                       good                                                                              good                                                                              good                                                                              good                                                                              good                                                                              good                                                                              good                                       __________________________________________________________________________     *Note:                                                                        Cooling temperature at the temperature region of 800 to 600° C.   

                                      TABLE 3                                     __________________________________________________________________________    Mill-hardened materials                                                                  Examples                                                           Number     15  16  17  18  19  20  21  22                                     __________________________________________________________________________    Composition wt %                                                              Be         0.98                                                                              0.98                                                                              1.3 0.81                                                                              1.08                                                                              1.3 0.92                                                                              1.05                                   Ni         0.52                                                                              0.4 0.49                                                                              0.32                                                                              0.31                                                                              0.1 0.46                                                                              0.45                                   Co         0   0.12                                                                              0   0   0   0.39                                                                              0   0                                      Al         0   2.1 0   2.0 2.0 2.0 1.9 1.9                                    Si         0.8 0.3 0.8 0   0   0.3 0   0                                      NiBe + CoBe                                                                              0.60                                                                              0.60                                                                              0.57                                                                              0.37                                                                              0.36                                                                              0.57                                                                              0.53                                                                              0.52                                   (theoretical value)                                                           NiBe + CoBe                                                                              0.35                                                                              0.40                                                                              0.35                                                                              0.20                                                                              0.22                                                                              0.37                                                                              0.35                                                                              0.32                                   (precipitated amount)                                                         Ratio of fine                                                                            91  72  59  62  86  60  81  75                                     particle (%)                                                                  Preparation                                                                   conditions                                                                    Solution treatment                                                                       905 895 890 910 905 880 910 905                                    temperature (°C.)                                                      Cooling temperature*                                                                     45  35  25  30  45  25  45  40                                     (°C./s)                                                                Aging temperature                                                                        340 340 340 340 340 340 340 340                                    (°C.)                                                                  Aging time (min)                                                                         15  60  45  20  20  30  20  30                                     Working ratio (%)                                                                        25  25  20  20  20  20  12  20                                     Properties                                                                    Stress relaxation                                                                        9   8   11  10  4   10  8   8                                      ratio (%)                                                                     Hardness (Hv)                                                                            240 290 257 240 259 290 289 291                                    Tensile strength                                                                         84.2                                                                              96.9                                                                              90.2                                                                              84.2                                                                              90.4                                                                              96.3                                                                              89.9                                                                              90.0                                   (kgf/mm.sup.2)                                                                Bending workability                                                                      ⊚                                                                  ◯                                                                     ◯                                                                     ⊚                                                                  ⊚                                                                  ◯                                                                     ⊚                                                                  ⊚                       (0°)                                                                   Bending workability                                                                      ⊚                                                                  Δ                                                                           ◯                                                                     ◯                                                                     ⊚                                                                  Δ                                                                           ⊚                                                                  ◯                          (90°)                                                                  Overall evaluation                                                                       very                                                                              very                                                                              good                                                                              good                                                                              very                                                                              good                                                                              very                                                                              very                                              good                                                                              good        good    good                                                                              good                                   __________________________________________________________________________     *Note:                                                                        Cooling temperature at the temperature region of 800 to 600° C.   

                  TABLE 4                                                         ______________________________________                                        Mill-hardened                                                                 materials                                                                              Comparative Examples (Component)                                     Number   1       2       3     4     5     6                                  ______________________________________                                        Composition                                                                   wt %                                                                          Be       0.47    0.47    0.47  0.47  1.06  1.06                               Ni       2       0.97    0     0.2   0.7   1                                  Co       0.47    0.5     0.97  0.77  0.69  0.39                               Al       0.2     1.5     0     3     3.5   0                                  Si       0       0.5     0.5   0.6   1.5   0.1                                NiBe + CoBe                                                                            1.70    1.70    1.12  1.12  1.60  1.60                               (theoretical                                                                  value)                                                                        NiBe + CoBe                                                                            0.78    0.50    0.25  0.75  1.15  0.75                               (precipitated                                                                 amount)                                                                       Ratio of fine                                                                          2       25      7     18    11    4                                  particle (%)                                                                  Preparation                                                                   conditions                                                                    Solution 915     905     915   905   890   905                                treatment                                                                     temperature                                                                   (°C.)                                                                  Cooling  1       15      5     10    5     2                                  temperature*                                                                  (°C./s)                                                                Aging temper-                                                                          380     380     380   380   360   360                                ature (°C.)                                                            Aging time                                                                             30      40      30    30    60    20                                 (min)                                                                         Working ratio                                                                          20      20      20    20    20    20                                 (%)                                                                           Properties                                                                    Stress   21      19      22    26    21    24                                 relaxation                                                                    ratio (%)                                                                     Hardness (Hv)                                                                          148     251     161   266   289   198                                Tensile  51.9    88.1    56.5  89.3  89.2  69.5                               strength                                                                      (kgf/mm.sup.2)                                                                Bending work-                                                                          ◯                                                                         X       ⊚                                                                    X     XX    Δ                            ability (0°)                                                           Bending work-                                                                          Δ XX      ◯                                                                       XX    XX    X                                  ability (90°)                                                          Overall  Poor    Poor    Poor  Poor  Poor  Poor                               evaluation                                                                             strength                                                                              work-   strength                                                                            work- work- strength                                            ability       ability                                                                             ability                                  ______________________________________                                         *Note:                                                                        Cooling temperature at the temperature region of 800 to 600° C.   

                  TABLE 5                                                         ______________________________________                                        Mill-hardened material                                                                     Comparative Examples (Component)                                 Number       7       8       9     10    11                                   ______________________________________                                        Composition wt %                                                              Be           1.54    1.56    1.69  1.69  1.05                                 Ni           0.2     0.11    1.1   0     0.15                                 Co           0.41    0.5     0.11  1.2   0                                    Al           0.1     1.5     0.2   0     0                                    Si           0.3     1       0     0.8   0.9                                  NiBe + CoBe  0.70    0.70    1.40  1.40  0.17                                 (theoretical value)                                                           NiBe + CoBe  0.43    0.46    1.05  1.02  0.09                                 (precipitated amount)                                                         Ratio of fine particle                                                                     40      21      38    12    65                                   (%)                                                                           Preparation                                                                   conditions                                                                    Solution treatment                                                                         870     860     865   860   905                                  temperature (°C.)                                                      Cooling temperature*                                                                       20      10      20    5     30                                   (°C./s)                                                                Aging temperature (°C.)                                                             340     340     345   345   350                                  Aging time (min)                                                                           40      60      40    15    15                                   Working ratio (%)                                                                          20      15      20    25    20                                   Properties                                                                    Stress relaxation                                                                          20      15      16    14    22                                   ratio (%)                                                                     Hardness (Hv)                                                                              254     290     265   288   201                                  Tensile strength                                                                           89.1    96.8    93    94.3  70.1                                 (kgf/mm.sup.2)                                                                Bending workability (0°)                                                            Δ XX      Δ                                                                             X     ⊚                     Bending workability                                                                        XX      XX      X     XX    ⊚                     (90°)                                                                  Overall evaluation                                                                         High    Poor    High  Poor  Poor                                              cost    work-   cost  work- strength                                                  ability       ability                                    ______________________________________                                         *Note:                                                                        Cooling temperature at the temperature region of 800 to 600° C.   

                                      TABLE 6                                     __________________________________________________________________________    Mill-hardened materials                                                                       Comparative Examples (Solution treatment)                                                         (Aging)                                   Number          12  13  14  15  16  17  18                                    __________________________________________________________________________    Composition wt %                                                              Be              1.04                                                                              1   0.9 1.29                                                                              0.7 1.04                                                                              1                                     Ni              1   0.87                                                                              0.8 0.6 0.2 1   0.87                                  Co              0.23                                                                              0   0.07                                                                              0.27                                                                              0.3 0.23                                                                              0                                     Al              0.6 0   1   0.5 2   0.6 0                                     Si              0.3 1   0   0.5 0.2 0.3 1                                     NiBe + CoBe (theoretical value)                                                               1.42                                                                              1.00                                                                              1.00                                                                              1.00                                                                              0.58                                                                              1.40                                                                              1.00                                  NiBe + CoBe (precipitated amount)                                                             0.95                                                                              0.85                                                                              0.61                                                                              0.58                                                                              0.41                                                                              1.15                                                                              0.85                                  Ratio of fine particle (%)                                                                    9   10  14  17  31  6   10                                    Preparation conditions                                                        Solution treatment temperature (°C.)                                                   845 860 855 860 855 905 900                                   Cooling temperature (°C./s)                                                            10  5   15  25  2   30  20                                    Aging temperature (°C.)                                                                360 350 350 340 340 270 280                                   Aging time (min)                                                                              30  15  10  15  35  120 100                                   Working ratio (%)                                                                             15  25  25  35  30  25  20                                    Properties                                                                    Stress relaxation ratio (%)                                                                   18  15  16  19  17  17  14                                    Hardness (Hv)   230 249 246 253 235 240 235                                   Tensile strength (kgf/mm.sup.2)                                                               81  87.2                                                                              86.5                                                                              88.9                                                                              82.6                                                                              83  81.2                                  Bending workability (0°)                                                               Δ                                                                           X   Δ                                                                           X   XX  ⊚                                                                  ⊚                      Bending workability (90°)                                                              X   X   X   XX  XX  ◯                                                                     ⊚                      Overall evaluation                                                                            Poor                                                                              Poor                                                                              Poor                                                                              Poor                                                                              Poor                                                                              Poor                                                                              Poor                                                  work-                                                                             work-                                                                             work-                                                                             work-                                                                             work-                                                                             strength                                                                          strength                                              ability                                                                           ability                                                                           ability                                                                           ability                                                                           ability                                       __________________________________________________________________________     *Note:                                                                        Cooling temperature at the temperature region of 800 to 600° C.   

                                      TABLE 7                                     __________________________________________________________________________                    Comparative Examples                                          Mill-hardened materials                                                                       (Aging)     Comparative Examples (Working ratio)              Number          19  20  21  22  23  24  25  26                                __________________________________________________________________________    Composition wt %                                                              Be              0.9 1.29                                                                              0.7 1.04                                                                              1   0.9 1.29                                                                              0.7                               Ni              0.8 0.6 0.2 1   0.87                                                                              0.8 0.6 0.2                               Co              0.07                                                                              0.27                                                                              0.3 0.23                                                                              0   0.07                                                                              0.27                                                                              0.3                               Al              1   0.5 2   0.6 0   1   0.5 2                                 Si              0   0.5 0.2 0.3 1   0   0.5 0.2                               NiBe + CoBe (theoretical value)                                                               1.00                                                                              1.00                                                                              0.58                                                                              1.42                                                                              1.00                                                                              1.00                                                                              1.00                                                                              0.58                              NiBe + CoBe (precipitated amount)                                                             0.75                                                                              0.65                                                                              0.50                                                                              0.86                                                                              0.61                                                                              0.55                                                                              0.67                                                                              0.30                              Ratio of fine particle (%)                                                                    13  23  20  19  11  31  49  10                                Preparation conditions                                                        Solution treatment temperature (°C.)                                                   910 885 905 905 900 910 885 905                               Cooling temperature* (°C./s)                                                           15  10  15  10  5   15  25  5                                 Aging temperature (°C.)                                                                420 400 300 360 350 350 340 340                               Aging time (min)                                                                              5   10  60  20  10  5   8   10                                Working ratio (%)                                                                             15  35  20  60  50  60  70  80                                Properties                                                                    Stress relaxation ratio (%)                                                                   14  18  17  15  11  13  16  13                                Hardness (Hv)   244 273 228 262 251 253 270 270                               Tensile strength (kgf/mm.sup.2)                                                               85.5                                                                              95.1                                                                              81.5                                                                              91.3                                                                              89.2                                                                              88.5                                                                              96.1                                                                              94.5                              Bending workability (0°)                                                               Δ                                                                           X   ⊚                                                                  X   Δ                                                                           X   X   XX                                Bending workability (90°)                                                              X   XX  ⊚                                                                  X   X   XX  XX  XX                                Overall evaluation                                                                            Poor                                                                              Poor                                                                              Poor                                                                              Poor                                                                              Poor                                                                              Poor                                                                              Poor                                                                              Poor                                              work-                                                                             work-                                                                             strength                                                                          work-                                                                             work-                                                                             work-                                                                             work-                                                                             work-                                             ability                                                                           ability ability                                                                           ability                                                                           ability                                                                           ability                                                                           ability                           __________________________________________________________________________     *Note:                                                                        Cooling temperature at the temperature region of 800 to 600° C.   

Example 2

This example relates to aging materials, in which cast pieces ofberyllium-copper alloys having the compositions each shown in Tables 8to 12 were subjected to solution treatment, finishing working and thenaging treatment under the conditions shown in said Tables to prepareproducts.

The results were examined for stress relaxation ratio, hardness, tensilestrength and banding workability of the thus obtained products, and arealso shown in Tables 8 to 12 with overall evaluations.

                                      TABLE 8                                     __________________________________________________________________________    Aging materials                                                                           Examples                                                          Number      1   2   3   4   5   6   7                                         __________________________________________________________________________    Composition wt %                                                              Be          0.9 0.7 1   0.9 1.11                                                                              1.11                                                                              1.29                                      Ni          0.6 0.8 0.87                                                                              0.8 0.27                                                                              0.4 0.6                                       Co          0   0.07                                                                              0   0.07                                                                              0.6 0.47                                                                              0.27                                      Al          0.5 1.5 1   1   0.9 0.2 0.5                                       Si          0.5 0.8 0   0   0.5 1   0.5                                       NiBe + CoBe 0.69                                                                              1.00                                                                              1.00                                                                              1.00                                                                              1.00                                                                              1.00                                                                              1.00                                      (theoretical value)                                                           NiBe + CoBe 0.60                                                                              0.74                                                                              0.73                                                                              0.69                                                                              0.71                                                                              0.71                                                                              0.76                                      (precipitated amount)                                                         Ratio of fine particles                                                                   92  48  62  71  59  61  50                                        (%)                                                                           Preparation                                                                   conditions                                                                    Solution treatment                                                                        910 905 900 910 900 900 885                                       temperature (°C.)                                                      Cooling temperature*                                                                      45  25  30  35  30  30  25                                        (°C./s)                                                                Aging temperature (°C.)                                                            340 360 345 350 345 345 340                                       Aging time (min)                                                                          300 100 180 120 90  90  120                                       Working ratio (%)                                                                         15  20  20  20  20  20  25                                        Properties                                                                    Stress relaxation                                                                         7   9   10  12  12  13  16                                        ratio (%)                                                                     Hardness (Hv)                                                                             283 330 297 286 325 322 356                                       Tensile strength                                                                          99.3                                                                              110 104 99.6                                                                              109 109 111                                       (kgf/mm.sup.2)                                                                Deformation amount (μm)                                                                3   4   5   4   4   4   6                                         Overall evaluation                                                                        very                                                                              good                                                                              good                                                                              very                                                                              very                                                                              very                                                                              good                                                  good        good                                                                              good                                                                              good                                          __________________________________________________________________________     *Note:                                                                        Cooling temperature at the temperature region of 800 to 600° C.   

                                      TABLE 9                                     __________________________________________________________________________    Aging materials                                                                           Examples                                                          Number      8   9   10  11  12  13  14                                        __________________________________________________________________________    Composition wt %                                                              Be          1.29                                                                              0.9 0.9 1.11                                                                              1.11                                                                              0.7 0.7                                       Ni          0   1.05                                                                              0   0.5 0.5 0.2 0.4                                       Co          0.87                                                                              0   1.05                                                                              0.55                                                                              0.55                                                                              0.3 0.1                                       Al          1.5 0.5 0.8 0   1   2   0.5                                       Si          0.9 1.2 0   0.6 1.1 0.2 0.9                                       NiBe + CoBe 1.00                                                                              1.21                                                                              1.21                                                                              1.21                                                                              1.21                                                                              0.58                                                                              0.58                                      (theoretical value)                                                           NiBe + CoBe 0.65                                                                              0.88                                                                              0.69                                                                              0.72                                                                              0.89                                                                              0.51                                                                              0.46                                      (precipitated amount)                                                         Ratio of fine particles                                                                   51  48  61  70  52  63  71                                        (%)                                                                           Preparation                                                                   conditions                                                                    Solution treatment                                                                        890 900 915 905 895 905 910                                       temperature (°C.)                                                      Cooling temperature*                                                                      25  25  30  35  25  30  35                                        (°C./s)                                                                Aging temperature (°C.)                                                            340 360 360 350 350 340 340                                       Aging time (min)                                                                          50  120 60  50  180 240 200                                       Working ratio (%)                                                                         35  30  18  36  25  20  20                                        Properties                                                                    Stress relaxation                                                                         15  12  12  15  11  12  13                                        ratio (%)                                                                     Hardness (Hv)                                                                             340 339 276 283 335 342 300                                       Tensile strength                                                                          109 107 96.8                                                                              99.9                                                                              111 110 105                                       (kgf/mm.sup.2)                                                                Deformation amount (μm)                                                                7   5   4   4   5   6   2                                         Overall evaluation                                                                        good                                                                              good                                                                              good                                                                              good                                                                              good                                                                              good                                                                              good                                      __________________________________________________________________________     *Note:                                                                        Cooling temperature at the temperature region of 800 to 600° C.   

                                      TABLE 10                                    __________________________________________________________________________    Aging materials                                                                           Examples                                                          Number      15  16  17  18  19  20  21                                        __________________________________________________________________________    Composition wt %                                                              Be          0.98                                                                              0.98                                                                              1.3 0.81                                                                              1.08                                                                              0.92                                                                              1.05                                      Ni          0.52                                                                              0.4 0.49                                                                              0.32                                                                              0.31                                                                              0.46                                                                              0.45                                      Co          0   0.12                                                                              0   0   0   0   0                                         Al          0   2.1 0   2.0 2.0 1.9 1.9                                       Si          0.8 0.3 0.8 0   0   0   0                                         NiBe + CoBe 0.60                                                                              0.60                                                                              0.57                                                                              0.37                                                                              0.36                                                                              0.53                                                                              0.52                                      (theoretical value)                                                           NiBe + CoBe 0.41                                                                              0.41                                                                              0.39                                                                              0.31                                                                              0.30                                                                              0.41                                                                              0.40                                      (precipitated amount)                                                         Ratio of fine particles                                                                   91  72  51  62  90  89  83                                        (%)                                                                           Preparation                                                                   conditions                                                                    Solution treatment                                                                        905 895 890 910 905 910 905                                       temperature (°C.)                                                      Cooling temperature*                                                                      45  35  25  30  45  45  40                                        (°C./s)                                                                Aging temperature (°C.)                                                            340 340 340 340 340 340 340                                       Aging time (min)                                                                          160 50  100 120 120 120 120                                       Working ratio (%)                                                                         25  25  20  20  20  12  20                                        Properties                                                                    Stress relaxation                                                                         7   5   8   8   4   4   4                                         ratio (%)                                                                     Hardness (Hv)                                                                             275 347 308 300 275 270 275                                       Tensile strength                                                                          96.5                                                                              112 106 104 96.0                                                                              95.9                                                                              96.4                                      (kgf/mm.sup.2)                                                                Deformation amount (μm)                                                                3   3   5   2   3   3   3                                         Overall evaluation                                                                        very                                                                              very                                                                              good                                                                              good                                                                              very                                                                              very                                                                              very                                                  good                                                                              good        good                                                                              good                                                                              good                                      __________________________________________________________________________     *Note:                                                                        Cooling temperature at the temperature region of 800 to 600° C.   

                  TABLE 11                                                        ______________________________________                                        Aging                                                                         materials                                                                              Comparative Examples                                                 Number   1       2       3     4     5     6                                  ______________________________________                                        Composition                                                                   wt %                                                                          Be       0.47    0.47    0.47  0.47  1.06  1.06                               Ni       1       0.97    0     0.2   0.7   1                                  Co       0.47    0.5     0.97  0.77  0.69  0.39                               Al       0.2     1.5     0     3     3.5   0                                  Si       0       0.5     0.5   0.6   1.5   0.1                                NiBe + CoBe                                                                            1.70    1.70    1.12  1.12  1.60  1.60                               (theoretical                                                                  value)                                                                        NiBe + CoBe                                                                            0.71    1.10    0.56  0.76  0.98  1.05                               (precipitated                                                                 amount)                                                                       Ratio of fine                                                                          2       29      9     38    10    21                                 particle (%)                                                                  Preparation                                                                   conditions                                                                    Solution 915     905     915   905   890   905                                treatment                                                                     temperature                                                                   (°C.)                                                                  Cooling  1       15      5     20    5     10                                 temperature*                                                                  (°C./s)                                                                Aging temper-                                                                          380     380     380   380   360   360                                ature (°C.)                                                            Aging time                                                                             60      120     100   100   60    300                                (min)                                                                         Working ratio                                                                          20      20      20    20    20    20                                 (%)                                                                           Properties                                                                    Stress   18      17      21    22    19    21                                 relaxation                                                                    ratio (%)                                                                     Hardness (Hv)                                                                          198     269     211   300   276   248                                Tensile  69.2    94.4    74    99.8  97.1  87                                 strength                                                                      (kgf/mm.sup.2)                                                                Deformation                                                                            2       4       2     15    17    3                                  amount (μm)                                                                Overall  Poor    Poor    Poor  Excess                                                                              Excess                                                                              Poor                               evaluation                                                                             strength                                                                              strength                                                                              strength                                                                            defor-                                                                              defor-                                                                              strength                                                          mation                                                                              mation                                   ______________________________________                                         *Note:                                                                        Cooling temperature at the temperature region of 800 to 600° C.   

                  TABLE 12                                                        ______________________________________                                        Aging materials Comparative Examples                                          Number          7       8        9     10                                     ______________________________________                                        Composition wt %                                                              Be              1.54    1.56     1.69  1.69                                   Ni              0.2     0.11     1.1   0                                      Co              0.41    0.5      0.11  1.2                                    Al              0.1     1.5      0.2   0                                      Si              0.3     1        0     0.8                                    NiBe + CoBe (theoretical value)                                                               0.70    0.70     1.40  1.38                                   NiBe + CoBe     0.47    0.50     0.97  0.91                                   (precipitated amount)                                                         Ratio of fine particle (%)                                                                    1       18       4     11                                     Preparation conditions                                                        Solution treatment                                                                            870     860      865   860                                    temperature (°C.)                                                      Cooling temperature (°C./s)                                                            1       10       2     5                                      Aging temperature (°C.)                                                                340     340      345   345                                    Aging time (min)                                                                              90      120      100   60                                     Working ratio (%)                                                                             20      15       20    25                                     Properties                                                                    Stress relaxation ratio (%)                                                                   18      13       13    13                                     Hardness (Hv)   295     298      301   310                                    Tensile strength (kgf/mm.sup.2)                                                               99.5    100      102   104                                    Deformation amount (μm)                                                                    11      15       18    20                                     Overall evaluation                                                                            Excess  Excess   Excess                                                                              Excess                                                 defor-  defor-   defor-                                                                              defor-                                                 mation  mation   mation                                                                              mation                                 ______________________________________                                         *Note:                                                                        Cooling temperature at the temperature region of 800 to 600° C.   

Example 3

An alloy cast piece comprising the composition containing 0.8% by weightof Be, 0.8% by weight of Ni, 0.07% by weight of Co and 1.0% by weight ofAl, and the balance being substantially Cu was subjected to hot workingand then cold working according to conventional method. After solutiontreatment at 910° C., the cast piece was immediately cooled to roomtemperature at a rate of 40° C./s. Then, after subjecting the cast pieceto finishing working with a working ratio of 20%, aging treatment wascarried out with various conditions.

The results of the tensile strength measured with respect to the thusobtained products are shown in FIG. 1.

It can be clearly seen from the figure that, in the present invention,good tensile strength can be obtained with wide aging treatmentconditions. Particularly, when it is carried out under preferredconditions at a temperature of 320° to 380° C., extremely excellenttensile strength could be obtained.

INDUSTRIAL APPLICABILITY

The beryllium-copper alloy of the present invention is advantageous inthat it has high strength and excellent bending workability, and yetdeformation amount at heat treatment is small even though the contentsof expensive Be is lowered than conventional products.

Also, the beryllium-copper alloy of the present invention has widetolerable aging treatment conditions, and as shown in FIG. 1, when it iswithin the temperature range of 320° to 380° C., even if the agingtreatment time is substantially changed in the range of 15 minutes to 6hours, change in tensile strength can be regulated within the range of±8 kgf/mm².

Therefore, the present invention provides advantages that not only anelectrically conducting spring material having excellent properties canbe realized economically, but also users' burden for aging treatmentcarried out by themselves can be markedly reduced.

We claim:
 1. A beryllium-copper alloy, comprising:0.5 to 1.5% by weightof Be; 0.3 to 1.5% by weight of at least one member selected from thegroup consisting of Ni and Co; 0.5 to 2.5% by weight of at least onemember selected from the group consisting of Si and Al; and the balancebeing substantially Cu; said alloy containing as an intermetalliccompound at least one of NiBe and CoBe in the range of 0.20 to 0.90% byweight, at least 45% thereof being present as fine particles having adiameter of 0.1 μm or less.